I've had my 2017Rex for about 3 months and the one irritation is the steering just as you've described. I wonder if having the self-parking extra makes any difference? I wouldn't describe the steering as 'light' but it's nothing like the many cars I've lived with over 55yrs driving.
My opinion, for what little it is worth, is that I think you will get used to the steering.
We have two i3's - one an i3 with self parking, and an i3S without self parking due to the wider track and wheel arches.
We have owned (leased then purchased) a series of i3's since 2016 - with our existing two purchased as low mileage used cars (the i3S had just 30 miles on it) are from 2019 and 2022 respectively and are pure BEV's (120Ah).
We have a farm, and I'm a 60 year old biker and former petrolhead, so I enjoy driving a lot of other stuff here. It ranges from tractors to a big diesel pickup and an old Landrover etc...
Until recently I also had a BMW 535i estate but sold it because it just wasn't getting used.
My i3S jkey is the one I usualy pick up for 98% of my road journeys.
None of these others have anything like the quick "go-kart" like steering of both the i3's - and which I have to say, on the smaller rural roads and in the town/city - I really prefer. The self park makes zero difference to that steering.
Only on faster, straighter roads (and particularly those with a rougher surface and a camber) do I think the steering feels a bit light and over assisted at times - but again you get used to it, and you do learn to treat it with care using minimal input.
I tend to use cruise control when on these roads - and that does seem to help a little - perhaps just because you concetrate more on the steering? I don't know...
That said, I think the speed of the steering response really saved me a year or so ago when driving on the motorway.
When coming up to the exit I wanted, I was doing about 60mph and slowly coming up behind a large pickup doing about 55mph loaded with what looked like rubble. I had already thought it would be unwise to stay behind it for any length of time (it was carrying along in the inside lane of the motorway) when, right on cue, as the uphill slip road for my exit was just metres away, a pretty large chunk of concrete complete with a bit of rebar (about 30cm x 30cm) fell off the side of the truck and bounced directly into my path at about head height.
Purely instinctively, I swerved VERY quickly left onto the hard shoulder, only just about retaining control (and then up the slip road) to avoid it - and to this day, I still don't know
how on earth I missed it... it remains a very sobering experience.
I do believe that in the 535, that chunk of concrete would have come in through the windscreen and joined me... possibly taking my head off. I doubt I would have been able to escape it - both due to the size of the car, but also because the steering was less "quick", although I had always considered it good.
So whilst I agree that some form of adjustment or coding adjustment on the steering assistance (or speed of steering) might be good, in the majority of normal situations I have encountered (and a once in a lifetime abnormal one) I am glad the i3 steering is how it is.